Many image-forming devices, especially fluid-ejection devices like inkjet-printing devices, form images on media on a media swath-by-media swath basis. For instance, an inkjet printer may move an inkjet printhead over a current swath of media, where the printhead ejects ink as it moves over the swath to form one swath of the image on the media. The media is then usually advanced so that the next swath of media is under the printhead, and the printhead moves over and ejects ink onto this new current media swath. This process is repeated until ink has been ejected onto nearly all the media swaths of a given sheet of media, to completely form an image on the media.
For image quality reasons, advancement of the media within the image-forming device is usually precisely controlled. Encoder signal generators may be used that provide signals based on how much the media has been advanced. That is, the generators sense mechanical motion and translate such motion into signals. However, there are various sources of error associated with encoders that can affect the accuracy with which position of the media can be determined.